A known integrated circuit package consists of accommodating semiconductor elements, ends of lead pieces introduced from the external side, and wires that electrically connect the semiconductor elements and the lead pieces together in a small cell that is air-tightly defined by an insulating substrate of a ceramics, a cap and a sealing glass. For instance, Japanese Patent Laid-Open No. 134852, 1984 entitled "Integrated Circuit Package" laid open on Aug. 2, 1984 exemplifies the use of a silicon carbide ceramic as an insulating substrate instead of the traditionally used alumina sintered product.
In such an integrated circuit package, however, cracks easily develop in a glass layer that seals the substrate and the cap, as disclosed in the above publication (page 2, right lower column, line 17 to page 3, left upper column, line 2).
To prevent the glass layer from being cracked, the above publication teaches the cap that is composed of a ceramic material having a coefficient of thermal expansion close to that of an insulating substrate composed of a silicon carbide ceramic.